The present invention is directed to response systems in which user responses entered in respective response units, also known as keypads, are retrieved at a base unit and, in particular, to such a response system in which the base unit acknowledges receipt of valid data from the response units.
One known form of response system utilizes time division multiplexing for organizing retrieval of user responses entered into response units, which are typically handheld units provided to a gathering of users. In such a system, a transmission by the base unit initiates a series of timeslots, each assigned to a particular response unit. Each unit having a selection entered by the user responds to the base unit transmission in its assigned timeslot. While pure time division multiplex systems accommodate the sending of data from the base unit to the response unit, such as data acknowledging receipt of valid data from particular response unit(s), it is not without limitation. For example, as the number of response units increase, the increase in assigned timeslots can excessively increase the duration between transmissions from the base unit.
Asynchronous response systems are also known. Timing of transmission from response units in an asynchronous response system is event driven, rather than controlled by the base unit. In particular, entry of a response by a user typically results in an immediate transmission of data from that response unit. Because more than one user may make an entry at the same moment, resulting in potential interference between transmissions, schemes have been devised for handling such data collisions. However, the asynchronous nature of the transmissions from the response units has made the acknowledging of validly received data by the base unit not practical.